As data storage densities in magnetic recording continue to progress in an effort to increase the storage capacity of hard disc drives, magnetic transition (bit) dimensions and recording head critical features are being pushed below 100 nm. In addition, making the recording medium stable at higher areal densities requires magnetically harder (high coercivity) storage medium materials. Traditionally, writing to a harder medium has been achieved by increasing the saturation magnetization, or 4πMs value, of the magnetic material of the inductive write head, thus bolstering the magnetic field applied to the medium. Though there has been some success in materials research efforts to increase Ms of the write head, the rate of increase is not sufficient to sustain the annual growth rate of bit areal densities in disc storage.
Another consequence of the rapid advance of areal densities is that write pole critical dimensions are decreasing faster than the corresponding Head-to-Media-Spacing (HMS). This presents a significant challenge to head design, as not only is the magnetic field strength effectively reduced, but the magnetic field profile at the media is more poorly confined, resulting in significant off-track fields that can cause undesirable effects such as adjacent track erasure, also referred to as side erasure. Thus, an important head design consideration is how to confine the magnetic fields more effectively without significantly degrading field strength at the media. A somewhat related issue is the need to shield the write head from the stray (or de-magnetization) fields of adjacent tracks, which can couple into the writer and interfere with the writing process.
Accordingly, there is a need for a magnetic recording head which is capable of overcoming the high coercivity of magnetic storage media, which confines the magnetic field produced at the write pole, and which shields the head from stray fields.